Electric circuit breaker



Sept. 15, 1942. c. THUMIM ELECTRIC CIRCUIT BREAKER Filed Aug. 22, 1940 Inventor": CaTl Thurnim,

His Attorney.

Patented Sept. 15, 1942 ES PATENT OFFICE ELECTRIC CIRCUIT BREAKER Carl Thumlm, Yeadon, Pa., assignor to General Electric Company, a corporation or New York Application August 22, 1940. Serial No. 353,883

lll Claims. '(Cl. 200-82) My invention relates to electric circuit breakers and more particularly to circuit breakers wherein relative movement between the contacts is produced by fluid-operated means.

It is a well-known fact that circuit breaker closing loads vary during the closing stroke, as a general rule being comparatively light at the beginning of the stroke and much heavier toward. the end of the stroke as the opening springs become charged and the contacts engage one another. Because of this tact, in the case of fluid-operated circuit breakers ii the cylinder at the fluid motor is sumciently large to produce enough operating force near the end of the closing stroke, it will be much too large and produce far too much force at the beginning of the closing stroke. As a result of designing such a cylinder large enough to produce suflicient force at the end of the closing stroke, enormous acceleration oi the apparatus will occur at the beginning of the closing stroke which is not only undesirable but may even cause damage to the circuit breaker operating mechanism. It is possible to provide a varying linkage between the fluid motor and the moving contacts of the circuit breaker to compensate for some of this discrepancy in the force applied during the closing stroke. However, circuit breakers are built in many diflerent sizes and it is not practical to provide difierent mechanisms ior each size 01 breaker. Accordingly, it would be desirable to provide an arrangement for varying the force applied to the closing mechanism oi the circuit breaker during the closing stroke which may readily be used on a variety of different circuit breaker sizes without requiring diflerent mechanisms for each breaker size.

It is an object of my invention, therefore, to provide a fluid-operated circuit breaker in which a variable force is applied to the circuit breaker operating mechanism to produce relative movement between the contacts without the use of varying ratio linkages or the like.

It is another object of my invention to provide a new and improved fluid-operated circuit breaker in which the fluid-operated means exerts a variable force during the closing stroke or the circuit breaker.

Further objects and advantages of m invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and torming a part of this specification.

For a better understanding or my invention, reference may be had to the accompanying drawing in which Fig. 1 is a schematic diagram partly in section of a fluid-operated circuit breaker embodying my invention, Fig. 2 is an enlarged cross-sectional view of a portion the apparatus illustrated in Fig. l in a diflerent operating position thereof, Fig. 3 is a modification of a portion of the apparatus illustrated in Fig. 2, Fig. 4 illustrates schematically a portion of an electric circuit breaker embodying a modification of my invention, and Fig. 5 is an enlarged crosssectional view 01' a portion of the apparatus 11- lustrated in Fig. 4.

Although my invention is applicable to any fluid-operated circuit breaker, single-phase or polyphase, for purposes of clearness and simplicity in the disclosure, I have illustrated my invention schematically in Fig. l as applied to a. fluid-operated circuit breaker ll of the cross gas-blast type comprising a stationary contact ll and'a movable contact I? arranged to be operated so as to draw an arc in an arc chute l3. It will be understood by those skilled in the art that contacts II and I! are arranged to be connected with suitable line terminals not shown. The stationary or fixed contact II is provided with spring-pressed contact fingers lid and longer arcing contact fingers l I, while movable contact i! is provided with an arcing tip i2 so that. when the contacts separate, an arc occurs between arcing tips II and i2. Immediately after separation of the contacts. one terminal or the arc is transferred by a blast of fluid, such as air or any other gas issuing from conduit it, which is suitably connected through a blast valve or the like, not shown. with a source of fluid under pressure, from contact lingers H to the contact II" which is provided with a tip of arc-resistant metal. The fluid blast from conduit it, upon the opening of circuit breaker ill, drives the are into the arc chute ll against the edges of a plurality of partitions II, which partitions are mounted in the arc chute l3 transverse to the arc gap and the ends of which extend close to the path or movement of the arcing tip I! of movable contact II. This circuit breaker I0 is illustrated by way of example only .in order to aid in understanding my invention, which is applied thereto. The circuit breaker'described thus far is not my invention but is described and claimed in United States Letters Patent 2,284,842, granted June 2, 1942, upon the joint application of David C. Prince, William K. Rankin, and Wilfred F. Skeats, and assigned to the same assignee as the present application.

It will be understood by those skilled in the art in view of the description following hereinafter that my invention is applicable to any fluid-operated circuit breaker whether fluid-operated means are either wholly or partially used to produce relative movement between the circuit breaker contacts. In the specific embodiment disclosed in Fig. 1, I have illustrated fluidoperated means which not only provide the force necessary to close circuit breaker ill but also provide the force necessary to charge the energystorage means which, in turn, provides the force required for opening the circuit breaker at the desired time. Accordingly, in Fig. 1, I have illustrated a fluid motor it which, acting through a trip-free thrust-transmitting mechanism generally indicated at 11, is arranged to close circuit breaker Ill and charge an energy-storage means illustrated as an opening spring II.

The mechanism for interconnecting the movable contact l2 of circuit breaker ill with fluid motor ii is illustrated as comprising an operating rod it, one end of which is operatively connected to movable contact l2 while the other end thereof is pivotally connected to one end of a suitable lever which is provided at the other end thereof with a crosshead 2|. This crosshead 2i is arranged to slide in a crosshead guide 22. A buil'er 23 may be provided adjacent the lever 20 in order to cushion the closing movement of the operating mechanism associated with circuit breaker Ill. Lever 20 has an intermediate point thereon connected to one end oi a suitable bell crank 2 which is pivotally mounted on a fixed support 25. A link 26, only a portion of which is shown, may be provided to interconnect bell crank with similar bell cranks, not shown, to operate other poles of the circuit breaker ID in the event that a polyphase breaker is provided, whereby simultaneous actuation of all the poles of the circuit breaker may be obtained.

The energy-storage means comprising spring i8 is suitably attached to operating rod i9 so, as

to supply the necessary force for producing uniform high-speed opening movement of circuit breaker in. Spring I8 is shown in the charged conditionin Fig. 1 when the circuit breaker HI is closed, and is arranged to cause clockwise rotation of bell crank 21 during the opening movement oi circuit breaker Ill.

Fluid motor it, which is provided to close the contacts of circuit breaker Ill as well as to charge energy-storage means i8, is illustrated as comprising a suitable cylinder 21 in which is reciprocatingly mounted a piston 28 operatively connected to a force-transmitting rod 29, the latter being arranged to engage with the trip-free thrust-transmitting linkage generally indicated at H. This thrust-transmitting linkage H has one end thereof connected to bell crank 21 so that force may be transmitted from piston 28 to operating rod l9 to close the contacts II and i2 of circuit breaker ID.

The fluid motor IS in Fig. 1 is shown at the instant when circuit breaker Ill has just been completely closed. Since this fluid motor is used only to close circuit breaker in and charge opening spring means l8, it is desirable to provide suitable means for returning piston 28 to its initial position at the left-hand end of cylinder 21 after the closing operation is completed. Accordingly, I have shown a suitable return spring mounted in a housing 3| supported by cylinder 21. Suitable ports 32 in housing 3! allow air in cylinder 21 at the right ofpiston 28 to escape when circuit breaker Ill is being closed.

The trip-tree thrust transmitting structure generally indicated at l'l may be of any suitable design, the one shown by way of example comprising a main toggle 23, 34 including a roller which coacts with the torque-transmitting rod 29 associated with piston 28. The toggle link 33 is pivotally connected at one end to a lever 26 supported on a flxed pivot 31. The

toggle link a, on the other hand, is connected at 28 to one end of a lever 39 supported on a fixed pivot to. The other end of lever 29 is connected through link II to hell crank 24. The pivot 42 of toggle link 33 is normally held fixed by a suitable tripping means including an extension 35' on lever 36 supporting a roller 43 which coacts with a tripping latch 44 pivotally mounted at 45. A solenoid-operated plunger 46 is provided to cause counterclockwise rotation oi tripping latch H and consequent release oi the trip-free mechanism generally indicated at H. When the toggle 23, 34 is straightened at its knee joint I! by forcetransmitting rod 29, the lever 29 is rotated about its fixed pivot 40 in a clockwise direction to cause operating rod I! to move downwardly to the position shown in Fig. 1 when the circuit breaker I0 is closed. Upon energlzation of solenoid -operated plunger 46, latch M is moved out of restraining engagement with respect to roller 42, and lever 36 is free to rotate in a counterclockwise direction by virtue of the force exerted by opening spring it. The toggle 22, 3| is then no longer in thrust-transmitting position and is free to collapse, permitting upward movement of operating rod I! under the bias of the energy-storage means comprising spring l8.

In Fig. l, the trip-tree thrust-transmitting linkage I1 is illustrated in a restraining or closed position with respect to operating rod is. In this position the knee joint 41 o! toggle 32, I4 is overset and engages a stop member 48. The linkage is thereby effectively locked in this position with respect to any opening thrust tending to move operating rod I9 upwardly as long as the pivot 42 of toggle link 33 is held fixed by the above-described tripping means. When latch 44 of the tripping means no longer restrains link 36 and, hence, alsopivot 42, the former rotates in a counterclockwise direction under the influence of the forces tending to cause opening movement or circuit breaker l0. When the toggle 83, 34 has collapsed and the lever 39 has rotated in a counterclockwise direction, circuit breaker I0 is opened by virtue oi the upward movement 01 the operating rod [9.

In order to operate fluid motor I6, I provide a source 49 of fluid under pressure which may, for example, be air under pressure. Fluid motor I6 is illustrated as being connected to source 48 through a suitable solenoid-operated valve 50. It will be understood by those skilled in the art thatsource 49 may also be connected to fluidblast conduit l4 through a suitable blast valve for supplying the necessary arc-extinguishing fluid in arc chute i3.

The circuit breaker operating mechanism illustrated in Fig. 1 is described in detail in my copending application, Serial No. 343,002, filed June 28, 1940, and assigned to the same assignee as the present application.

In order to obtain a variation in the force applied to the operating mechanism or circuit breaker in during the closing stroke, I provide a variable orifice means, generally indicated at ii, at the fluid pressure inlet 21' of cylinder 21. By virtue of this variable orifice means it, shown in detail in Fig. 2, a relatively small force is' applied to the operating mechanism of circuit breaker in during the initial portion 0! the closing stroke so as to avoid excessive acceleration thereof, while a much larger force is applied during the latter part of the closing stroke when the energy-storage means comprising spring II is almost fully charged and contacts H and I2 begin to engage. The variable orifice means ii is shown in the initial position in Fig. 2 prior to closure of the circuit breaker II while, in Fig. 1, this variable orifice means is shown in the position which a portion thereof assumes at the end of the closing stroke prior to the return of piston 28 to its initial position. The variable orifice means Ii comprises a housing 52 in which is slidably mounted a metering pin 3. Metering pin SI has one end thereof initially held against piston 28 by light spring 54. This end of metering pin 53 adjacent piston II is reduced in diameter as shown at ii to provide a clearance space It between metering pin II and the inlet I1 to cylinder 21 so that clearance space 56 provides a restricted area for the flow of fluid under pressure, from source is to fluid motor 28, and limits this flow so that a relatively small force, sufiicient only to operate piston II at the beginning of the closing stroke, is available. By properly proportioning the clearance space 58, the initial forces applied will not be excessive so as to cause damage to the operating mechanism of circuit breaker Ill. As the piston 2| moves toward the right of cylinder 21 during the closing stroke of ciricuit breaker Ill, spring Bl initially and later the fluid under pressure cause metering pin it to follow the movement of piston 28. A plurality of flutes 56 cut in metering pin it greatly increase the area of the inlet 21' tocylinder 21 as the closing stroke of circuit breaker l progresses so that a sufficiently increased force for charging the energy-storage means and the like is available. It will be understood that the point at which flutes 58 become eflectlve may be varied by using diil'erent metering pins 53 to agree with the required action. This change of metering pins can readily be accomplished by removing plug 61 provided in the end of chamber 52. It will be obvious to those skilled in the art that, in the arrangement just disclosed, no means need be'provided for moving the metering pin 53 other than light spring 54 which initiates this movement, after which the fluid pressure continues to cause this metering pin to follow the movement of piston 28.

It will be understood by those skilled in the art that metering pin 53 instead of being provided with a portion of reduced cross section 55 may be provided with a suitable slot 50 (Fig. 3) properly dimensioned to supply the necessary fluid tor the initial operation of fluid motor It. Such an arrangementis disclosed in Fig. 3, which is self-explanatory, the corresponding parts 0! this metering pin being designated by the same reference numerals as in Fig. 2.

The operation of the apparatus disclosed in Figs. 1 and 2 will be obvious to those skilled in the art in view of the detailed description included above. In order to initiate the closing stroke, solenoid-operated valve ill interconnects source 49 and cylinder Tl of fluid motor it. with the metering pin 53 initially in the position indicated in Fig. 2, a minimum force. determined by the design of the metering pin, is applied to piston 28 by virtue of the reduced area 56 through which fluid under pressure may enter cylinder 21. As the closing operation of circuit breaker Iii progresses. the flutes 56 on metering pin it become eflective and the inlet opening to cylinder 2! increases so that the increased force required for charging spring means it and cansing engagement of contacts II and I2 is available. In the event that energization of solenoidoperated plunger It occurs to trip circuit breaker it during the closing operation thereof, the tripfree mechanism will collapse and allow highspeed opening of circuit breaker iii. In addition to conserving fluid and preventing initial excessive acceleration, variable orifice means iialso serves as a means for cushioning the return of piston It for, as metering pin it is returned to its initial position shown in Fig. 2, the inlet opening to cylinder Ildecreases in size, thereby producing a sort or dashpot efl'ect.

Although I have thus far described a particular type bf variable orifice means, it will be obvious that other forms and arrangements may be used. In Fig. 4, for example, I have shown a portion of the circuit breaker and operating mechanism of Fig. l with the corresponding parts thereof designated by the same reference numetals, in which a modified variable orifice means is disclosed. Referring now to Fig. 4 and Figs. 4 and 5 comprises a sliding plate ill including a large opening ii and a smaller opening 62. Sliding plate III is arranged to reciprocate between a pair of members 63 forming the housing of the variable orifice means 59 and each having an enlarged opening 6| therein arranged to be connected with conduits 5|) and 21", respectively. -Suitable sealing means may be provided between sliding plate 80 and members 53 to prevent the escape of fluid.

-Plate 60 is illustrated in Fig. 4 as being arranged to reciprocate in response to the closing movement of circuit breaker Iii so that, at the initiation of the closing stroke, small orifice 62 is in alignment with openings 64 while, as the closing operation progresses, large opening 6| comes into operation in a manner very similar to the operation of metering pin 53 of Figs. 1 to 3 described heretofore. In order to relate the movement of sliding plate Gil with the movement of circuit breaker iii, sliding plate 60 is pivotally connected at 86 with a lever 61 pivotally mounted at 6B. The other end of lever 61 is connected to pivotally mounted lever 39 through link 69.

In Figs. 4 and 5, the apparatus is shown at the instant circuit breaker III is completely closed and the large orifice BI is in the operative position. In the event of trip-free operation of the circuit breaker ill, lever 39 is rotated to return plate 88 immediately to its initial position so that 7 small orifice 82 is in operative position, whereupon the flow of fluid to cylinder 21 is reduced, resulting in a conservation of fluid and, at the same time, providing a dashpot effect to lessen the force with which the unloaded piston returns to its initial position. The operation of the apparatus disclosed in Figs. 4 and 5 will be obvious i. In an electric circuit breaker ompr sing a plurality of relatively movable contacts, a fluid motor including a piston for producing relative movement between said contacts, a source of fluid under pressure, means for interconnectin said source and said fluid motor, and means (or varying the flow of fluid between said source and said fluid motor during an operating stroke of said circuit breaker, said fluid motor being so constructed and arranged with reference to said last-mentioned means as to permit said fluid under pressure to act initially on substantially the entire working face of said piston.

2. In an electric circuit breaker comprising a plurality of relatively movable contacts, fluidoperated means for producing relative movement between said contacts, a source of fluid under pressure, means for interconnecting said source and said first-mentioned means, and means for gradually varying the force applied by said fluid under pressure on said first-mentioned means during an operating stroke of said circuit breaker starting with substantially zero force.

3. In a fliiid operated electric circuit breaker comprising a pair of relatively movable contacts a fluid motor for operating said circuit breaker, a source of fluid under pressure, means for in terconnecting said source and said fluid motor for producing relative movement between said contacts, and means permitting the force transmitted from said source of fluid under pressure to said fluid motor to increase after a predetermined closing movement of said circuit breaker has occurred, said last-mentioned means being incapable of transmitting substantially any force from said fluid under pressure acting thereon to said fluid motor.

4. In an electric circuit breaker comprising a pair of relatively movable contacts, a fluid mo: tor for operating said circuit breaker, a source of fluid under pressure, means including a valve for controlling the flow oi fluid between said source and said motor to produce relative movement between said contacts, and means interposed between said valve and said fluid motor for varying the amount of fluid supplied during the time said fluid motor produces relative movement between said contacts, said last-mentioned means being incapable of transmitting substantialiy any force from said fluid under pressure acting thereon to said fluid motor.

5. In an electric circuit breaker comprising a pair of relatively movable contacts, a, fluid motor for producing relative movement between said contacts, a source of fluid under pressure, means interconnecting said source and said fluid motor for closing said circuit breaker, and a variable orifice means interposed between said source and said fluid motor to vary the force applied by said fluid motor to said circuit breaker during the closing stroke thereof including a metering -pin having a plurality of flutes thereon and having one end thereof cooperating with said fluid motor.

6. In an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor including a piston for producing relative movement between said contacts, a source of fluid under pressure, means for interconnecting said source and said fluid motor for closing said cir cuit breaker, and means interposed between said source and said fluid motor for preventing excessive acceleration of the movable parts of said circuit breaker during the initial part of the closing operation, said fluid motor being so constructed and arranged with reference to said last-mentioned means as to permit said fluid under pressure to act initially on substantially the entire working face of said piston.

7, In an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure, means for interconnecting said source and said fluid motor for closing said circuit breaker, and a variable orifice means interposed between said source and said fluid motor to prevent excessive acceleration of the movable parts of said circuit breaker during the closing operation thereof and for conserving fluid under pressure during a tripfree operation of said circuit breaker.

8. In a fluid-actuated electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure, means for interconnecting said source and said fluid motor for closing said circuit breaker, and a variable oriflce means interposed between said source and said fluid motor operable in response to the relative movement between said contacts for preventing excessive acceleration of the movable parts of said circuit breaker during the closing operation thereof, said last-mentioned means being incapable of transmitting substantially any force from said fluid aider pressure acting thereon to said fluid mo- 9. In a fluid-actuated electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure, means for interconnecting said source and said fluid motor for closing said circuit breaker, and a variable oriflce means interposed between said source and said fluid motor to prevent excessive acceleration of the movable parts of said circuit breaker during the closing operation thereof comprising a sliding plate provided with a plurality of openings of diflerent sizes, said plate being movable in response to the relative movement between said contacts so that said different sized openings therein successively become eflective during the closing operation of said circuit breaker.

10. In a fluid-actuated electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor including a piston for producing relative movement between said contacts, a source of fluid under pressure, means including a valve for interconnecting said source and said fluid motor for closing said circuit breaker, and a variable oriflce means interposed between said source and said fluid motor to prevent excessive acceleration of the movable parts of said circuit breaker during the closing operation thereof including a metering pin reciprocally mounted and operable in response to the opera tion of said fluid motor to vary the size of the fluid inlet theretmsaid metering pin being constructed so as to transmit a force directly to said piston upon opening of said valve which is insumcient to move said piston.

CARL TI-IUMIM.

DISCLAIMER 2,296,071.Oarl Thum'im, Yeadon, Pa. ELECTRIC Cmcm'r BREAKER. Patent dated September 15, 1942. Disclaimer filed November 27, 1944, by the assignee, General Electric Company. Hereby enters this disclaimer to claims 1, 4, and 6 of said patent.

[Ofiic'ixd Gazette December 26, 1944.] 

